Blue line at top of clip

Now, I know my workflow is all wrong, but I have an issue with videos I've 'letterboxed'. What I've done is manually 'squash' a 1280x720 video (by clicking on one of the four anchor points at each corner and pulling up), to create black space at the top and bottom.

Trouble is a blue line appears at the very top of the video (but not at the bottom, as you can see in the image), both in the preview and the exported video.

a) Yeah, like I said, my workflow is all wrong... I didn't want to remove the top and bottom of the footage when letterboxing - nor did I want black borders on the side - so just squashed the frame to create the effect. Doubtless there's a smarter way to do it, but it looks fine for my purposes.

b) I'm so happy you asked me how I captured it. Great logic; I've gone back to the clips that have the issue and it's all from a single source. I've then doubled back to the original capture (via mepgstreamclip, if memory serves) and there it is - the blue line at the very top of the clip.

Why do you need it letterboxed at all? Is it to fit in with other footage in a letterboxed project?

If you want the letterboxed look then maybe a sort of compromise would also fix the line problem. That blue line might always be there on recapture, as stuffing hidden data in there would not normally be noticed, so... you could try a combination of squashing and putting letterbox bars top and bottom.

You could either create a Black Plane, then mask out the centre section - or make two thin planes and place them individually at the top and bottomm of the screen. Then partially squash the footage and put it behind the planes to obscure a little more. Enough to clip off the blue line and as much as you can get away with that doesn't cut into logos, text and other crucial info etc. which would end up looking less squashed and weird.

As @Palacono indicated, that edge is normally hidden in the overscan area of old TVs. It could be data, but more likely it's just chromatic aberration from being copied a time or two on old video decks. I doubt that recapturing will get rid of it, as it's pretty much baked-in on the source. If it were me, I wouldn't worry about it, as it's just part of what comes with old footage like this (just like the color bleed and overall lack of definition). If it really bugs you that much, though, here's another way to approach fixing it. Turn each of these old clips into a composite shot, making sure the comp dimensions match those of the clip. Inside each comp, scale up the footage ever so slightly. 101% might be enough. Yes, it crops off a fraction of the other edges as well, but now you can use that comp wherever you want and the oddly-colored top edge isn't an issue.

While I can appreciate your desire to create a sense of "otherness" with these captured clips (and by "otherness" I'm guessing that you simply mean that you want these old clips to stand out in some obvious way compared to other footage in the montage), I don't know that non-uniform scaling is the way to go. I'm not even talking about the end letterbox effect. I'm simply talking about the fact that the content feels squashed in one direction more than another. Maybe I'm in the minority, but watching squashed footage always bugs me. I'm too drawn to the unnatural proportions of things, and it takes me out of the moment.

If you want a simple way to make this footage stand out without the unnatural squash, here's an idea. Drop your footage into a composite shot (if you used the edge-killing tip above, you'll drop that comp into yet another comp). In this new comp, duplicate your footage/comp layer, so now you have two copies of the same thing. Take the top copy and scale it down (uniformly) to something like 80%. On the bottom copy, reduce the opacity to about 30-40%. With that bottom copy being full-size, you won't have black edges around your top layer, yet the whole two-layer treatment definitely makes it stand out. To add some variation, try adding an effect or two to the bottom layer. Maybe desaturate it. Maybe add a blur. Maybe do both. In the end, you have something that definitely feels different while maintaining normal proportions.

Ah bless you for your interest. I ended up using a transparent background that I then letterboxed and dragged across the sequence of clips that needed to feel 'different'. A minimal amount of scaling was then applied to remove the blue line.